KR200153720Y1 - A dynamic focus circuit of monitor - Google Patents

Abstract

The present invention relates to a dynamic focus circuit that stabilizes a focus signal by stabilizing a high voltage used to form a dynamic focus signal.

The circuit of the present invention forms a parabolic waveform by receiving a horizontal synchronous signal and a vertical synchronous signal, and loads the parabola waveform at a high voltage input from an FBT and applies it to the dynamic focus circuit of the monitor through the FBT. A circuit for stabilizing a high voltage input from an FBT to provide a DC high voltage to the parabolic waveform comprises: rectifying means (D3, C3) for rectifying and smoothing a high voltage pulse input from the FBT; If the output voltage is increased accordingly the voltage between the base-emitter increases to increase the collector current, on the contrary, if the output voltage decreases, the control transistor (Q5) to reduce the collector current by reducing the voltage between the base-emitter; And when the collector current of the control transistor is increased, the base current is decreased to increase the resistance component. Accordingly, the output voltage of the rectifying means is decreased. When the collector current of the control transistor is decreased, the base current is increased to decrease the resistance component. Therefore, it is composed of a voltage adjusting transistor Q6 which stabilizes the voltage by increasing the output voltage of the rectifying means.

Description

Dynamic Focus Circuit of Monitor

The present invention relates to a dynamic focus circuit for compensating for a shift in focus when scanning the edge of a screen in a monitor. In particular, the present invention relates to a dynamic focus circuit that stabilizes a focus signal by stabilizing a high voltage used to form a dynamic focus signal. It is about.

In general, a color display device (CPT) used for a monitor focuses and accelerates hot electrons emitted from R, G, and B guns and collides with R, G, and B fluorescent surfaces through a point on a shadow mask to form pixels, and is vertical. And a sawtooth current flowing through the horizontal deflection coil to form a two-dimensional screen.

In order to operate the color display device CPT, a heater voltage of about 6.3V is applied to the heater, and a focus grid voltage, a screen grid voltage, etc. are required to focus the emitted hot electrons, and an anode is used to accelerate the hot electrons. A high pressure of about 20 KV will be applied.

In this case, the focus grid for focusing the electron beam emitted from the cathode may be divided into a static focus (S.FOCUS) grid and a dynamic focus (D.FOCUS) grid. Signal is called a dynamic focus signal.

Since the dynamic focus signal applied to the focus grid is typically a high voltage of several hundred volts, the dynamic focus signal is generated after the parabolic waveform signal is generated and loaded on the high voltage input from the FBT.

However, since the high voltage input from the FBT is unstable and fluctuates in magnitude, the parabola waveform loaded on the fluctuating high voltage also fluctuates so that the dynamic focus signal becomes unstable.

Accordingly, the present invention has been proposed to solve the above problems, and has an object to provide a dynamic focus circuit that is capable of generating a stable dynamic focus signal by stabilizing a high voltage input from the FBT.

In order to achieve the above object, the circuit of the present invention receives a horizontal synchronous signal and a vertical synchronous signal to form a parabola waveform, and loads the parabola waveform to a high voltage input from an FBT and applies the dynamic focus grid through the FBT. A dynamic focus circuit of a monitor, comprising: rectifying means for rectifying and smoothing a high voltage pulse input from said FBT to stabilize a high voltage input from said FBT to provide a DC high voltage to said parabola waveform; If the output voltage is increased accordingly the voltage between the base-emitter increases to increase the collector current, on the contrary, if the output voltage is reduced, the control transistor for reducing the collector current by reducing the voltage between the base-emitter; As the collector current of the control transistor increases, the base current decreases to increase the resistance component. Accordingly, the output voltage of the rectifying means decreases. When the collector current of the control transistor decreases, the base current increases to decrease the resistance component. Therefore, it is characterized by comprising a voltage adjusting transistor for stabilizing the voltage by increasing the output voltage of the rectifying means.

1 is a block diagram showing a general dynamic focus circuit in a monitor;

2 is a view illustrating a general dynamic focus;

3 is a circuit diagram illustrating a dynamic focus circuit according to the present invention;

4 is an operational waveform diagram in each part shown in FIG. 3.

* Explanation of symbols for main parts of the drawings

100: dynamic focusing circuit 101: synchronization processing unit

102: waveform control signal generator 103: focus signal generator

104: buffer 105: parabolic output

106: gain adjustment unit 110: power supply (SMPS)

120: DC-DC converter 130: horizontal oscillation and drive unit

140: horizontal output unit 150: horizontal deflection coil

160: FBT

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As is well known, the diameter of the electron beam in the CRT increases toward the periphery of the screen. In other words, the focus at the edge is wider than the focus at the center of the monitor, so the sharpness is poor at the edge. To compensate for this, high-resolution monitors apply a compensation waveform (called a dynamic focus signal) so that the electron beam focuses exactly on the fluorescent surface of the CRT.

This compensation waveform depends on the combination of the CRT and the deflection coil. Usually, the larger the screen of the CRT, the higher the voltage peak required for compensation. Therefore, a dynamic focus signal having a function of correcting a difference in focus caused by a difference in driving distance between the center portion of the CRT and the surroundings of the CRT requires several hundred volts of power, and such power is usually obtained from an FBT.

Here, the horizontal dynamic focus signal for compensating the left and right edges of the screen is a signal of a parabolic waveform in which the center portion generated by the horizontal period 1H is concave, as shown in FIG. The vertical dynamic focus signal for compensating the upper edge and the lower edge is a parabolic waveform signal in which the center portion generated by the vertical period 1V is concave, as shown in FIG. At this time, the voltage of the crest value at the edge portion increases as the CRT screen increases as described above, but is generally 300V _{PP to} 500V _{PP in the} horizontal case and 100V _{PP to} 150V _{PP in the} vertical case.

In the focus signal of the waveform, the horizontal focus signal is repeated with respect to the horizontal period, and the vertical focus signal is repeated with respect to the vertical period and applied to the dynamic focus grid.

Meanwhile, as shown in FIG. 1, a general dynamic focusing circuit for generating a dynamic focusing signal having a parabola waveform includes a synchronization processor 101, a waveform control signal generator 102, a focus signal generator 103, and a buffer ( 104, a parabolic output section 105, and the dynamic focus signal generated in this circuit is input to the FBT 150 and applied to the dynamic focus grid of the CRT together with the DC voltage. In addition, the primary winding of the FBT 150 receives a DC voltage from a power supply 110 (SMPS), provides a DC voltage to the DC-DC converter 120, a horizontal output unit 140, and a horizontal deflection coil 145: H. DY) is connected, and the horizontal output unit 140 allows sawtooth current to flow in the horizontal deflection coil 145 according to the output of the horizontal drive unit 130. In this case, a high voltage (about 800 V DC in the embodiment of the present invention) for loading the parabola waveform generated by the focus signal generator is input to the parabola output unit 105 from the FBT 160.

Referring to the operation of the dynamic focus circuit, the synchronization processor 101 is implemented as an exclusive OR gate, and receives the horizontal sync signal H.sync and the vertical sync signal V.sync regardless of the polarity of the input sync signal. The horizontal and vertical synchronization signals of a single polarity are output, and the waveform control signal generator 102 is implemented with a plurality of multivibrators (eg, 74LS123) generating a start signal and an end signal according to the horizontal and vertical synchronization signals.

The focus signal generator 103 generates the focus signal of the parabola waveform by the start signal of the waveform control signal generator and ends the generation of the focus signal by the end signal. At this time, in the case of a multi-sync monitor, the magnitude of the crest value Vpp of the parabola waveform can be adjusted by the operation of the gain adjusting unit 106.

The buffer 104 is typically implemented as a transistor circuit, and generates a dynamic focus signal by adding the horizontal parabola waveform and the vertical parabola waveform signal generated by the focus signal generator, and the parabola output unit 105 outputs the dynamic focus signal. Amplification to high voltage is applied to the dynamic focus grid of the CRT with the DC voltage through the FBT (150).

Here, the circuit of the present invention for loading the parabola waveform generated by the focus signal generator to the DC high voltage input from the FBT, as shown in Figure 3, the transistor (Q1) for amplifying the horizontal and vertical parabola waveform of the focus signal generator ), A transistor (Q4, Q3) for blanking the focus signal, a transistor (Q2) for loading a parabola waveform at a high voltage, and a high voltage stabilizer (200).

In addition, the high voltage stabilization unit 200 includes a diode D3 rectifying the high voltage input from the FBT, a control transistor Q6 for controlling the output voltage, and a voltage regulation transistor Q5 for stabilizing the output voltage according to the output of the control transistor. It is composed of

Referring to FIG. 3, at node ⓐ, a relatively low focus signal, in which horizontal and vertical parabola waveforms are combined, is shown as shown in FIG. 4A, and at node ⓑ, as shown in FIG. 4B. The focus signal combined with the blanking signal appears. That is, since the dynamic focus signal is related to the display area, it is necessary to appropriately adjust the blanking area.

At node ⓒ, as shown in Fig. 4C, a high voltage pulse of about 1000 Vp-p is input from the FBT, and at node ⓓ, a parabolic waveform is loaded at a high voltage as shown in Fig. 4D. The focus signal appears and is applied to the dynamic focus grid via FBT.

In this case, the dynamic focus signal has a difference of about 430 Vp-p between the center and the edge on the horizontal side and about 150 Vp-p between the center and the edge on the vertical side.

As described above, the dynamic focus circuit according to the present invention stabilizes the DC high voltage input from the FBT and loads the parabolic waveform signal to generate the dynamic focus signal, thereby stabilizing the dynamic focus signal.

Claims (1)

A dynamic focus circuit of a monitor configured to receive a horizontal synchronous signal and a vertical synchronous signal to form a parabola waveform, and to load the parabola waveform at a high voltage input from an FBT and apply the parabolic waveform to a dynamic focus grid through the FBT. A circuit for stabilizing a high voltage input from the FBT to provide a DC high voltage to the parabolic waveform, Rectifying means (D3, C3) for rectifying and smoothing the high voltage pulse input from said FBT; If the output voltage is increased accordingly the voltage between the base-emitter increases to increase the collector current, on the contrary, if the output voltage decreases, the control transistor (Q5) to reduce the collector current by reducing the voltage between the base-emitter; And When the collector current of the control transistor is increased, the base current is decreased to increase the resistance component. Accordingly, the output voltage of the rectifying means is decreased. When the collector current of the control transistor is decreased, the base current is increased to decrease the resistance component. Accordingly, the dynamic focus circuit of the monitor, characterized by comprising a voltage adjusting transistor (Q6) to stabilize the voltage by increasing the output voltage of the rectifying means.